In recent years, the use of plastics in vehicular applications, both automotive and truck, has increased remarkably. The increased plastic usage has been due primarily to the necessity to reduce the overall weight of vehicle, together with the elimination of expensive machined or die cast metal components. Automative requirements place stringent demands upon the plastic materials used in vehicles, but perhaps the most stringent demands are those for under-the-hood uses. Conditions within the engine compartment are particularly difficult due to the temperature variations which may be encountered. Temperatures may run as high as 400.degree. F. and as low as -50.degree. F.
One typical example is a conduit extending through a truck engine compartment to connect an exterior air cleaner or filter to the engine air intake. Such a conduit is exposed to the widely variant temperatures within the engine compartment, while at the same time it must be able to withstand the collapsing forces exerted thereon if the air filter were to be completely blocked by accreted contaminants while the engine is still running and drawing a vacuum in the conduit. Prior to the present invention, such conduits were machined steel castings, due to the stringent strength-at-temperature requirements.
It would be desirable to manufacture such a conduit by blow molding from a plastic composition, if a composition could be provided having the necessary high melt point, tensile strength, flexural strength and ability to resist deflection at elevated temperatures.